Prior art and technical background which invention is based:
Developments in electro-optics for communications, sensor engineering, data storage and control and regulating technology are presently tending increasingly toward microminiaturization and integrated electro-optics. Until now, a miniaturization of laser sources was only possible in the area of semiconductor lasers. The reduction in size of the construction of solid-state lasers has been hindered by the poor efficiency of the conversion of electrical power into laser light, the size of the excitation sources, discharge lamps of the optical bank and individual optical elements which are still manufactured in the classical manner of construction.
The size of the optical head of continuous wave lasers in the power range of 1-100 W in conventional construction is typically 10.times.10.times.20 cm and the power supplies with cooling units have a weight of 10-100 kg, depending on the power range. This size of device and especially the poor efficiency greatly impedes the integration of lasers in various systems, e.g. in medicine, material processing, holography, display technology and measuring technology, and is one of the significant reasons for the relatively limited use of lasers in these fields.
A miniaturization of solid-state lasers is desirable not only for this reason; it would also considerably facilitate the use of automated manufacturing methods of lasers and laser components.
Laser diodes with GaAlAs semiconductors have been commercially available for a few years; they are constructed as an array in the range of 100 mW to several Watts optical continuous output and are suitable for exciting solid-state lasers. The first laser of this type is the diode-pumped Nd:YAG laser with the emission line .gamma.=1.06 .mu.m which is distinguished by an electric-optical efficiency approximately 10 times higher than that of lasers conventionally excited by discharge lamps.
The advantage of converting the radiation of a laser diode into the radiation of a solid-state laser consists in the considerably improved beam quality of the latter and its low spectral bandwidth. An improvement by a factor of more than 10.sup.6 is achieved here with reference to the spectral radiation density.
Diode-pumped solid-state lasers are described e.g. in the periodical "Laser and Optoelectronics" [Laser und Optoelektronik] 20 (3)/1988, pages 56-67.
Although these lasers represent clear progress in the direction of an increase in efficiency and miniaturization, the additional structural component parts such as laser mirror, microsystem, cooler, beam switcher and imaging lens system are still manufactured with conventional techniques which hardly enables a significant reduction in size. Its size exceeds that of the base elements such as the laser diode array, e.g. with dimensions of 22.times.100 .mu.m and the laser crystal with 2.times.5 mm, e.g. by an order of magnitude.
A simple and economical solution to the cooling of a laser diode and other optical/electronic components is currently one of the most urgent problems for miniaturization and is an object of the invention, as is the integration of the latter in a suitable mounting.
The coolers for the laser diodes, which are usually provided as Peltier, radiant or liquid coolers, are many times greater and more massive than the diode housing, e.g. of size T03. The diode housing itself, with a diameter of 100 mm, is many times larger than the diode chip itself, which has a diameter of 1 mm. In this case also, a more simple and economical solution is sought for.
A peculiarity of the laser diode-pumped solid-state laser consists in that the spectral position of the emission lines of the diode must be adapted exactly to the most effective absorption line of the laser material. This is presently achieved by means of correct doping of the semiconductor. Since the emission wavelength of the semiconductor is also dependent on the temperature, the temperature must be readjusted by means of the diode, depending on the adjusted electrical current. The output of the solid-state laser itself is usually used as a measurement variable for regulating, and the temperature of the diode is readjusted to the maximum output of the laser. It is necessary to regulate a second time in order to keep the output of the laser diode as stable as possible. In this instance, the optical power of the diode is measured and readjusted during a possible change in current. The two regulating circuits overlap one another and must be tuned to one another.